Previous digital communication systems either provided for a fixed configuration of bus structure or provided an external manual switching mechanism. The fixed configurations suffer the disadvantage of being very restrictive. Data communications between devices in this type of network are restricted to a single bus structure unless resort is made to expensive, time consuming system cable reconnections. The communication systems utilizing external switching also suffer from being very expensive and also from being very bulky. The external switches in these type of systems may very well be larger than the equipment which they are switching.
The purpose of the digital reconfigurable data bus module is to provide data communication among digital equipments such as computers, memories, displays, sensors or peripherals in a fixed physical structure but in a reconfigurable electronic bus structure. The significant advantage of the digital reconfigurable data bus module then is to provide for this restructuring without any physical change in cabling or externally initiated switching. Previous data buses provided the characteristics of only one type of structure without physical changes in cabling or externally initiated switching.
Several previous communication systems disclose the ability to connect and reconnect different devices to one another. For example, U.S. Pat. No. 3,024,418 shows a selective coupling apparatus for use in connecting several utilization devices to a single signal source. However, here the device allows the reconnection of the multiple utilization devices in only one bus configuration, in this case a tree structured bus. Also, U.S. Pat. No. 3,399,380 discloses an interconnection network in the nature of a crosspoint switch. However, the unit connection network provides only switching means and more importantly only a single point switching means for interconnecting any of a first set of terminals to any of a second set of terminals and does not provide the capability of switching bus configurations, since more than a single point switch is required.
Several previous communication systems describe combination loop and serial communication means, for example U.S. Pat. No. 3,742,144 discloses an interconnected loop digital transmission system to which means are provided for switching between multiple system loops. However, in this system the bus structure is fixed in a multiple loop configuration and cannot be changed. The only switching involved is switching between already-existing loops. Also, U.S. Pat. No. 3,879,582 shows a loop digital data communication system. However, again the bus configuration is fixed in the established loop configuration. U.S. Pat. No. 3,904,829 discloses a demand driven multiplexing system which provides a combination closed loop communication link along with a serially arranged communication link. However, although both loop and serial configurations are disclosed in one communication system, there exists no method of changing the loop and serial systems. Again, the bus structure is fixed. Previous communication systems also utilized the ability to insert different types of data processing units in one communication loop. In U.S. Pat. No. 3,879,582 a loop controller is inserted in the loop in order to control the data processing function. The loop controller, however, provides merely basic timing and delay functions and does not significantly alter data format.